The present invention relates to hydrogels, in particular gels for use on wounds.
It is known (Winter, G. D. 1962, Nature 193, pp 293–294) that healing under an occlusive dressing which maintains a moist environment is significantly better than using dry dressings, or leaving a wound open to the atmosphere.
The concept of moist healing has been applied to the management of both acute and chronic wounds. This has resulted in a significant improvement in the outcome of healing in wounds that were, by their very nature, difficult to heal. As a consequence of this, the wound care industry has seen an increase in the number of occlusive dressings designed specifically to maintain a moist wound environment. At the forefront of this technology has been the development of hydrogel dressings.
These hydrogel dressings are water and polymer combinations designed to create and/or maintain a hydrophilic microenvironment over the wound surface. The gel is in intimate contact with the wound surface, and absorbs exudate into the hydrophilic layer of gel. This prevents an accumulation of fluid at the wound surface yet keeps the cells moist. It has been demonstrated that this moist wound environment is optimal for re-epithelisation and fibroplasia.
Hydrogels can also donate water to desiccated tissue and are very useful in re-hydrating dry eschar and slough, thereby encouraging autolytic debridement. Other advantages of hydrogels are that they allow free passage of water vapour and oxygen, and the low adhesion of the gel to the wound surface allows easy removal (usually by irrigation) without damage to the underlying newly formed tissue.
Hydrogel systems for use in wound care have been described by, for example, Agren, M. S. in Acta. Derm. Venereol. 1998, 78:119–122
The problem with such known hydrogels is that exposure to fluid released from the wound causes an exponential reduction of viscosity of the gel, leading to loss of gel integrity and, if left in place on the wound, will exacerbate tissue (both wound and normal skin) maceration. Therefore, dressing changes have to be undertaken frequently to prevent this problem, which is both time consuming and expensive.